Project Summary Emerging adults and youth living with HIV 18-29yo (YLWH) are the least likely of any age group to engage in care or achieve virologic suppression, and Southern YLWH live at the epicenter of the modern U.S. HIV epidemic. In Texas, molecular clusters of rapid HIV transmission among youth highlight missed opportunities including delays in care engagement and virologic suppression, and less than 20% of YLWH in our target population in South Texas achieve virologic suppression. Our long-term goal is to improve rates of virologic suppression for YLWH through development of a novel mobile health (mHealth) tool for care engagement. mHealth interventions, such as smartphone applications (apps), are rapidly adopted by youth, and are an underutilized resource in increasing care engagement for YLWH. This project proposes to adapt and pilot test the efficacy of an existing mHealth tool, the PositiveLinks Program (PL), developed by Dillingham and Ingersoll (Co-Is). Pl is a multimodal intervention, including daily adherence assessment, appointment reminders, secure messaging with clinic providers, and an online anonymized peer support network. PL increased care engagement and virologic suppression in adults (majority >40yo) with HIV in observational studies, but has not been studied in YLWH. Formative research by Taylor (PI), Nijhawan (Co-I), and Villarreal (Co-I) showed that patients and providers in Texas seek relational interventions and YLWH request mHealth approaches for engagement. We will use the Theory of Planned Behavior (TPB) as a theoretical model and Positive Youth Development (PYD) as an approach to rigorously adapt and pilot test a modified version of PL, PositiveLinks for Youth (PL4Y). To do so, we will conduct a rigorous formative evaluation of PositiveLinks to adapt it to the needs of YLWH, including: semi-structured interviews informed by TPB with YLWH experiencing challenges with care engagement and stakeholders, and feedback from a Youth Advisory Board (Aim 1). We will then develop and iteratively adapt components of PL and new youth-focused components emerging from the formative evaluation with YLWH who are newly diagnosed, disengaged in care, or not virologically suppressed using a human-centered design approach informed by PYD to generate PositiveLinks for Youth (PL4Y) (Aim 2). Finally, we will conduct a small pilot randomized control trial of the adapted PL4Y program in YLWH disengaged from or newly engaging in HIV care to assess its impact on virologic suppression (Aim 3). A mixed methods process evaluation will assess acceptability and feasibility of this novel intervention. Through these aims we will develop an innovative care engagement tool that caters to the developmental and socio/structural needs of YLWH. Our approach can serve as a model for efficient adaptation of mHealth interventions to new target audiences in response to an urgent community need.